Below roughly minus 5 degrees Celsius exhaust, condensate on the cold side of a recovery core freezes. Frost blocks channels, raises pressure drop and silently drops effectiveness. Frost control is mandatory in cold climates.
Three proven strategies
| Method | How it works | Best for |
|---|---|---|
| Supply preheat | Warm incoming air before the core so exhaust stays above freezing | Plate and heat pipe |
| Exhaust bypass | Divert part of exhaust around the core when frost risk is high | Plate |
| Thermal wheel | Warm wheel section melts frost as it rotates | Rotary |
Practical notes
- Preheat uses a little energy but protects winter recovery, often the lowest-lifecycle-cost fix.
- Bypass modulates with outdoor temperature; size the control to avoid comfort dips.
- Wheels self-defrost but leak a little carryover, not for separated-stream duties.
Frost interacts with effectiveness and flow arrangement; factor it into sizing from the start.
Specifying a unit for your project?
EN159 builds plate, rotary, heat-pipe and counterflow air-to-air exchangers with frost-protected options. Send airflow (m3/h), inlet temperatures and available space and we will size it.
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